Morphotaxonomy, genetic affinities and ecology of Australian and Antarctic populations of the potentially fish killing, heterotrophic dinoflagellates Cryptoperidiniopsis brodyi and Pfiesteria piscicida

• Main Author: Park, T-G
• Format: Thesis
• Language: English
• Published: 2006
• Subjects: Dinoflagellates; Shellfish; Oysters; Antarctic; Antarc*
• Online Access: https://eprints.utas.edu.au/21138/; https://eprints.utas.edu.au/21138/1/whole_ParkTae-Gyu2007_thesis.pdf

The heterotrophic dinoflagellate Cryptoperidiniopsis brodyi and closely related species were investigated from Australia-wide marine environments with regard to their morphology, phylogenetic relationships, interactions with shellfish larvae, and natural abundance. Nine isolates of C. brodyi and two isolates of Pfiesteria piscicida were collected and cultured from Australia and ballast water originating from Indonesia. Scanning electron microscopy (SEM) and molecular sequence analyses of SSU, LSU, ITS, and 5.8S rDNA regions revealed that Australian C. brodyi strains have identical morphological features but include two different genetic variants. Isolates of C. brodyi from Australia, comprised the two ITS genotypes A and B which diverged 16.2% and 6.6%, respectively, of the ITS genotype from the U.S. type locality. Genotype A was widespread whereas genotype B thus far has only been found in Tasmania. Pfiesteria piscicida was cultured from ballast water indicating a potential inflow of foreign harmful algae into Australian waters. Previous studies using PCR-based assays claimed a wide distribution of Pseudopfiesteria shumwayae in Australia including in Brunswick River in Western Australia. However, isolates from the Brunswick River samples were identified in the present work as C. brodyi. Nonspecific reactions from P. shumwayae SSU rDNA-based primers were confirmed with Australian C. brodyi. This suggests that P. shumwayae presence in Australia has been overestimated by previous molecular detection methods. A species-specific real-time PCR assay using the TaqMan\(^®\) probe system was developed for rapid detection and quantification of C. brodyi in environmental samples. Specific PCR primer-probes for C. brodyi were designed against the ITS2 rDNA regions and tested for selectivity, specificity and sensitivity of detection. The assay was able to detect the presence of less than 1 cell per PCR reaction, did not respond to non-target species, and accurately quantified C. brodyi in natural water samples. This assay ...